Chemoenzymatic Production of Enantiocomplementary 2-Substituted 3-Hydroxycarboxylic Acids from l-α-Amino Acids

A two-enzyme cascade reaction plus in situ oxidative decarboxylation for the transformation of readily available canonical and non-canonical l-alpha-amino acids into 2-substituted 3-hydroxycarboxylic acid derivatives is described. The biocatalytic cascade consisted of an oxidative deamination of l-alpha-amino acids by an l-alpha-amino acid deaminase from Cosenzaea myxofaciens, rendering 2-oxoacid intermediates, with an ensuing aldol addition reaction to formaldehyde, catalyzed by metal-dependent (R)- or (S)-selective carboligases namely 2-oxo-3-deoxy-l-rhamnonate aldolase (YfaU) and ketopantoate hydroxymethyltransferase (KPHMT), respectively, furnishing 3-substituted 4-hydroxy-2-oxoacids. The overall substrate conversion was optimized by balancing biocatalyst loading and amino acid and formaldehyde concentrations, yielding 36-98% aldol adduct formation and 91-98% ee for each enantiomer. Subsequent in situ follow-up chemistry via hydrogen peroxide-driven oxidative decarboxylation afforded the corresponding 2-substituted 3-hydroxycarboxylic acid derivatives.

Automated summary

This study presents a two-enzyme cascade reaction plus in situ oxidative decarboxylation method for transforming both common and uncommon l-alpha-amino acids into 2-substituted 3-hydroxycarboxylic acid derivatives. The biocatalytic cascade achieved high substrate conversion and enantiomeric excess, with subsequent in situ oxidative decarboxylation leading to the final products.